I happen to disagree with getting rid of the riffling of the deck if it's natural for him to do that.
I too riffle the back of my deck when I execute a pass, it's never been a problem for me or noticed though because I often just toy with the deck like that; it's just the way I handle cards.
I agree that there shouldn't really be any superfluous movements, but if such movements are in accordance with how you handle the deck when you're not doing anything, then I see no problem.
In saying this, I can see why you would want it to be a 'simple action of squaring up the deck' but sometimes the deck is already square, what happens then? Possible interesting discussion I think but not for this thread perhaps.
- Sean